a) Field of the Invention
The invention is directed to a vacuum valve comprising a valve housing which has an inlet opening and an outlet opening which penetrate opposite walls of the valve housing, a valve seat surrounding the inlet opening, and a closure unit which is arranged in an interior space of the valve housing and which has a valve plate which is adjustable between an open position in which it releases the inlet opening, an intermediate position in which it covers the inlet opening but is lifted from the valve seat, and a closed position in which it covers the inlet opening and is pressed against the valve seat, and at least one adjusting piston which is arranged in an interior space of the closure unit and, for the purpose of adjusting the valve plate between its intermediate position and its closed position, is displaceable in direction of its longitudinal center axis between a passive position in which the valve plate is in its intermediate position and an active position in which the valve plate is in its closed position. At least one work space of the closure unit that can be acted upon by pressure gas for displacing at least one adjusting piston into its active position is bounded by a diaphragm seal.
b) Description of the Related Art
A vacuum valve in which a valve plate is displaceable between its intermediate position and its closed position by means of an adjusting piston arranged in an interior space of a closure unit is known from U.S. Pat. No. 6,561,484 B2. The closure unit comprises the valve plate and a supporting plate. The valve plate and the supporting plate can be anchored against the valve housing between the inner surfaces of the valve housing in the area around the inlet opening and the outlet opening by means of the adjusting piston. A receiving housing for the adjusting piston can be arranged at the supporting plate or at the valve plate. Sealing rings acting between the adjusting piston and the receiving housing are provided for forming work spaces which are acted upon by pressure to displace the adjusting piston. At least one sealing bellows extends between the valve plate and the supporting plate in some of the embodiment forms. In addition to embodiment forms in which the closure unit is displaceable linearly for adjusting between its open position and its intermediate position, embodiment forms constructed in the manner of a pendulum valve are also described. In these embodiment forms, the carrying arm at which the closure unit is arranged is swivelable around a swiveling axis for displacing the closure unit between its open position and its intermediate position.
Another valve in which a valve plate is displaceable between its intermediate position and its closed position by means of a adjusting piston arranged in an interior space of a closure unit is known from US 2004/0079915 A1. In this case also, work spaces which can be acted upon by pressure gas for displacing the adjusting piston are sealed by flexible sealing rings.
U.S. Pat. No. 6,776,394 B2 discloses a pendulum valve in which cylinder bore holes in which adjusting pistons are arranged are formed in the valve housing. Tappets can be displaced by the adjusting pistons in order to press the valve plate against the valve seat in the closed position of the valve plate. The adjusting pistons are likewise sealed relative to the walls of the cylinder spaces by sealing rings.
A vacuum valve of the type mentioned above is known from the embodiment example shown in FIG. 5 of DE 19 857 201 A1. Tensioning cylinders serve as lifting bodies for pressing valve plates against a valve housing. The tensioning cylinders are sealed relative to a base body of the closure unit by diaphragm seals.
It is known from U.S. Pat. No. 5,975,492 A to press valve plates against valve seats of the valve housing by means of an actuator arranged in an interior space of the closure unit. The actuator comprises plates which are pressed together so as to be tight against pressure by high-grade steel bellows (see FIG. 21).
Further, adjusting elements with diaphragm pistons are known from other applications as vacuum valves, for example, in automobile engineering in connection with brake cylinders or in fixture construction for clamping parts, i.e., workpieces to be clamped.